The need for improved food preservation methods is great. It has been estimated that about one quarter of the word's food supply is lost as a result of microbial spoilage and food-borne microbial infections represent a constant and serious threat to human health.
Several bacterial species that may contaminate and grow in foodstuffs and crops are pathogenic or produce toxins and cause a range of food-poisoning diseases. Despite substantial improvement in the technology and hygiene, food products may be exposed to spoilage and pathogenic bacteria in the food-handling environment and the number of food poisoning is still increasing in most of the countries.
Fungal spoilage can lead to serious economic losses. Several food products e.g. agricultural products, dairy and meat products, fruits and vegetables and derived products, bakery products and cosmetics are very susceptible to fungal growth. Examples of dairy products are cheese, cottage cheese, ricotta and yogurt. Dried cured sausages are an example of meat products. Examples of agricultural products are crops such as cereals, nuts, fruits, vegetables and flower bulbs. Spoilage by fungi does not only affect the quality of the product, but also represents a health risk. It is well known that some fungal species, which grow on e.g. dairy products and sausages, can produce mycotoxins. Some mycotoxins are extremely dangerous as they can cause lethal diseases. Therefore the outgrowth of unwanted fungi in and on food products should always be prevented.
Food preservation techniques, e.g. heat processing, freezing, ultrasound, irradiation, and modified atmosphere packaging, significantly reduce microbial load but of particular concern is the evidence that processed foods are being contaminated with microorganisms following processing and prior to packaging. Of rinsing concern in the food industry is microbial spoilage of various foods such as dairy and meat products, dressings, spreads, margarines and seafood. Especially food products in the 2.0 to 7.0 pH range are known to be susceptible to microbial spoilage by yeast, mould, acid tolerant bacteria and/or mesophilic or thermophilic spore forming and non-spore forming bacteria.
Mostly, processed foods are not eaten directly after processing thereby permitting bacteria, yeast or mould introduced by post-contamination to grow. Since food consumption may occur without reheating the processed foods to sufficient temperatures for sufficient time, there is a risk of food poisoning or food spoilage. Furthermore, the recent trend for minimally processed foods with the intrinsic nutritional and sensory qualities of raw and fresh foods has raised a new safety risk. Milder preservation treatments, such as high hydrostatic pressure and pulsed electric fields have been proved to be successful but rely on effective hurdles i.e. cold chain and addition of natural anti-microbials.
There has been extensive research conducted in the field of food safety to develop effective anti-microbial compositions, which function as anti-fungal and anti-bacterial compositions.
In U.S. Pat. No. 5,895,680 by Cirigliano et al., the preservative system including natamycin and nisin is stated. The instability of aqueous natamycin solution is compensated by increased natamycin concentrations. In U.S. Pat. No. 5,895,680 it is taught that natamycin has to be present in amount of at least 1.5 times the maximum solubility based on the water content present in the foodstuff. The reason behind this is that it is believed that soluble natamycin is not stable in aqueous surroundings and that therefore always solid (for example crystal or amorphous) natamycin has to be present for the anti fungal activity.